Method for making carbon nanotube composite preform

ABSTRACT

A method for making a carbon nanotube composite preform includes following steps. A substrate is provided. Carbon nanotubes are formed on the substrate. The carbon nanotubes and the substrate are placed in a solvent for a predetermined time. The carbon nanotubes and the substrate are drawn from the solvent. The carbon nanotubes and the substrate are dried.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 12/002,116, filed on Dec. 14, 2007, entitled, “CARBON NANOTUBE COMPOSITE PREFORM AND METHOD FOR MAKING THE SAME,” which claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 200710076745.6 filed on Aug. 31, 2007 in the China Intellectual Property Office. The disclosures of the above-identified applications are incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The invention relates to a preform and method for making the same, particularly, to a carbon nanotube composite preform and a method for making the same.

2. Discussion of Related Art

Carbon nanotubes (CNT) are a novel carbonaceous material and received a great deal of interest since the early 1990s. Carbon nanotubes have interesting and potentially useful electrical and mechanical properties. Due to these and other properties, it becomes an important application direction for CNTs to be used as fillers in engineering materials.

Nowadays, the method for growing a CNT array on a substrate, such as a glass, silicon, or heat-resistant metal substrate has matured. CNT arrays are in widespread use, such as in field emission tubes, ultra-thin flat panel displays, cathode electrodes, biosensors and so on.

However, naturally occurring gas-filled spaces between CNTs in CNT arrays lead to poor radial properties (such as thermal conductivity) and thus affect the properties of the whole material. So it is beneficial to fill gaps between CNTs in the CNT array with metals or polymer materials to make a composite material. This ensures the composite material has improved radial properties.

Conventionally, the CNT composite material is made by directly infiltrating the melting metal or polymer material into the CNT array. Referring to an article by H. Huang entitled “Aligned Carbon Nanotube Composite Films for Thermal Management” (Adv Mater., Vol 17, 2005, p 1652), the above-described manufacturing process is reported. However, the gaps between the CNTs in the CNT array are so small that some materials, such as indium, copper, etc., cannot infiltrate the CNT array well.

What is needed, therefore, is a CNT composite preform with filterable gaps between CNTs and a simple, low cost, and short cycle method for making the described CNT composite preform.

SUMMARY

In one embodiment, a CNT composite preform includes a substrate and a plurality of CNTs formed thereon. Each CNT includes a first end adjacent to the substrate and a second end away from the substrate. Gaps between the second ends of the CNTs are bigger than gaps between the first ends. The method for making the CNT composite preform includes the following steps: (a) providing a substrate; (b) forming a plurality of CNTs (e.g., a CNT array) on the substrate; (c) placing the CNTs and the substrate in a solvent for some time; (d) drawing the CNTs and the substrate from the solvent; (e) drying the CNTs and the substrate to form a CNT composite preform.

Other advantages and novel features of the present CNT composite preform and the related method for making the same will become more apparent from the following detailed description of present embodiments when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present CNT composite preform and the related method for making the same can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present CNT composite preform and the related method for making the same.

FIG. 1 is a flow chart of a method for making a CNT composite preform, in accordance with a first embodiment.

FIG. 2 is a cross-sectional schematic view of the CNT composite preform of FIG. 1.

FIG. 3 shows a Scanning Electron Microscope (SEM) image of the second ends of the CNTs which are away from the substrate, after vacuum treatment process in oxydol solution, in accordance with the first embodiment.

FIG. 4 shows a Scanning Electron Microscope (SEM) image of a cross-sectional surface of the CNT composite preform parallel to the CNT axis, after vacuum treatment process in oxydol solution, in accordance with the first embodiment.

FIG. 5 shows a Scanning Electron Microscope (SEM) image of the first ends of the CNTs which are near the substrate, after vacuum treatment process in oxydol solution, in accordance with the first embodiment.

FIG. 6 shows a Scanning Electron Microscope (SEM) image of the second ends of the CNTs after vacuum treatment process in water, in accordance with a second embodiment.

FIG. 7 shows a Scanning Electron Microscope (SEM) image of the second ends of the CNTs after vacuum treatment process in ethanol solvent, in accordance with a third embodiment.

FIG. 8 shows a Scanning Electron Microscope (SEM) image of the second ends of the CNTs after ultrasonic vibration treatment process in oxydol solution, in accordance with a fourth embodiment.

FIG. 9 shows a Scanning Electron Microscope (SEM) image of the second ends of CNTs after being removed from water, in accordance with a fifth embodiment.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one preferred embodiment of the present CNT composite preform and the related method for making the same, in at least one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made to the drawings to describe, in detail, embodiments of the carbon nanotube (CNT) composite preform and the related method for making the same.

Referring to FIG. 1, a method for making a CNT composite preform includes the following steps: (a) providing a substrate; (b) forming a CNT array on the substrate; (c) placing the CNT array and the substrate in a solvent for some time; (d) drawing the CNT array and the substrate from the solvent; (e) drying the CNT array and the substrate to form a CNT composite preform.

In step (a), the substrate is made of at least one material selected from a group consisting of glass, silicon, metal, and metal oxide. The substrate has at least one surface. In step (b), the CNTs are formed by chemical vapor deposition method or laser ablation method. A diameter of each CNT in the CNT array is in the approximate range from 1 to 100 nanometers. A length of the CNTs in the CNT array is in the approximate range from 1 to 500 micrometers. In the embodiments, the maximum height of the CNT array is about 200 micrometers. The gaps between CNTs in the CNT array are in the approximate range from 1 to 100 nanometers. The CNTs are single-walled CNT, double-walled CNT, or multi-walled CNT.

Step (c) further includes the substeps of: (c1) supplying a solvent; (c2) placing the solvent in a container; (c3) placing the CNT array and the substrate in the solvent for some time.

In step (c1), the solvent includes at least one substance selected from a group consisting of water, ethanol and oxydol solution. A mass concentration of the oxydol solution is about 25%. The amount of the solvent is, usefully, enough to immerse the CNT array therein. In step (c3), the immersion time is in an approximate range from 10 to 60 minutes.

Step (c) further includes a substep of vacuum treatment or ultrasonic vibration treatment to evacuate the gas between the CNTs in the CNT array. In the vacuum treatment process, a water-cycle vacuum pump is used to evacuate the gas. The vacuum treatment process takes about 10˜60 minutes. Alternatively, the ultrasonic vibration treatment takes about 10˜60 minutes. During the aforementioned processes, the gas between the CNTs in the CNT array migrates to the ends of the CNT array away from the substrate and forms gas pockets. As a function of the surface tension of the gas pockets, the ends of the CNTs away from the substrate are shifted to form honeycomb-shaped gaps. The size of the gaps is in the approximate range from 2 to 300 micrometers.

In step (e), the drying treatment is conducted in a vacuum drying oven at about 40° C.˜50° C. to vaporize the solvent in the CNT array. The drying time is in the approximate range from 10 to 60 minutes.

Referring to FIG. 2, the CNT composite preform 10 prepared by the aforementioned method includes a substrate 102 and a CNT array 110 formed thereon. The CNT array 110 includes first ends 104 of the CNTs being adjacent to the substrate and second ends 106 of the CNTs being away from the substrate. Gaps between the second ends 106 of the CNTs are bigger than the gaps between the first ends 104 thereof.

The CNTs in the CNT composite preform 10 are aligned, with unique physical properties, and are easy to handle. The CNT composite preform 10 can be applied to a variety of fields, such as electronic materials, thermal materials, optical materials, magnetic materials, catalyst materials, for example. The CNT composite is, beneficially, combined with the metal or polymer composites, e.g., penetration of the metal or polymer material into the CNT composite perform 10. Due to the size of the gaps between the second ends 106 of the CNTs is in the approximate range from 2 microns to 300 microns, the metal or polymer material can easily penetrate the CNT array via the aforementioned gaps. Thus, better performing composites can be produced.

The following examples are provided by way of illustration to show how the present CNT composite preform 10 can be prepared, and should not be construed as limiting the invention in any way.

Example (1): First, a substrate 102 is provided 1 centimeter long and 1 centimeter wide; second, a CNT array 110 is formed thereon; third, the CNT array 110 and the substrate 102 are placed in an oxydol solution with a mass concentration of 25% and the solution is vacuum treated for 20 minutes; fourthly, the CNT array 110 and the substrate 102 are removed from the solution; and finally, the CNT array 110 and the substrate 102 are dried in a vacuum drying oven to form a CNT composite perform 10. The Scanning Electron Microscope (SEM) image of the second ends 106 of the CNTs which are away from the substrate 102 and the cross-section of the CNT preform parallel to the CNT array 110 axis and the first ends 104 of the CNTs which are near the substrate 102 are shown in FIG. 3, FIG. 4, and FIG. 5 respectively. Gaps between the second ends 106 of the CNTs, which are bigger than the gaps between the first ends 104 of the CNTs, can be seen in FIG. 3 to be in an approximate range from 10 to 30 microns.

Example (2): First, a substrate 102 is provided 1 centimeter long and 1 centimeter wide; second, a CNT array 110 is formed thereon; third, the CNT array 110 and the substrate 102 are placed in water and the solution is vacuum treated for 40 minutes; fourth, the CNT array 110 and the substrate 102 are removed from the solution; and finally, the CNT array 110 and the substrate 102 are dried in a vacuum drying oven to form a CNT composite perform 10. The Scanning Electron Microscope (SEM) image of the second ends 106 of the CNTs is shown in FIG. 6. The sizes of the gaps between the second ends 106 thereof, as can be seen in FIG. 6, are in an approximate range from 15 to 30 microns.

Example (3): First, a substrate 102 is provided 1 centimeter long and 1 centimeter wide; second, a CNT array 110 is formed thereon; third, the CNT array 110 and the substrate 102 are placed in an ethanol solvent and the solution is vacuum treated for 60 minutes; fourth, the CNT array 110 and the substrate 102 are removed from the solution; and finally, the CNT array 110 and the substrate 102 are dried in a vacuum drying oven to form a CNT composite preform 10. The Scanning Electron Microscope (SEM) image of the second ends 106 of the CNTs is shown in FIG. 7. The sizes of the gaps between the second ends 106 thereof, as can be seen in FIG. 7, are about 300 microns.

Example (4): First, a substrate 102 is provided 1 centimeter long and 1 centimeter wide; second, a CNT array 110 is formed thereon; third, the CNT array 110 and the substrate 102 are placed in an oxydol solution with a mass concentration of 25% and the solution is ultrasonically vibrated for 30 minutes; fourth, the CNT array 110 and the substrate 102 are removed from the solution; and finally, the CNT array 110 and the substrate 102 are dried in a vacuum drying oven to form a CNT composite preform 10. The Scanning Electron Microscope (SEM) image of the second ends 106 of the CNTs is shown in FIG. 8. The sizes of the gaps between the second ends 106, as can be seen in FIG. 8, are in an approximate range from 2 to 5 microns.

Example (5): First, a substrate 102 is provided 1 centimeter long and 1 centimeter wide; second, a CNT array 110 is formed thereon; third, the CNT array 110 and the substrate 102 are placed in water for 40 minutes; fourth, the CNT array 110 and the substrate 102 are removed from the water; and finally, the CNT array 110 and the substrate 102 are dried in a vacuum drying oven to form a CNT composite preform 10. The Scanning Electron Microscope (SEM) image of the second ends 106 of the CNTs is shown in FIG. 9. The sizes of the gaps between the second ends 106, as can be seen in FIG. 9, are in an approximate range from 10 to 200 microns.

The CNT composite preform and the method for making the same have the following virtues: first, the gaps between the CNTs away from the substrate 102 are penetrable, having a size in the approximate range from 2 microns to 300 microns, thus the CNTs can easily combine with the metal or polymer to form a composite; second, the methods of the present embodiments have little effect on the properties of the CNT array 110, and the CNTs in the CNT array 110 are aligned; and finally, the methods are simple, easy to implement, low cost, and consume little time.

It is to be understood that the carbon nanotube array in the above-described embodiments can be any kind of a plurality of carbon nanotubes formed on the substrate and preferred orientated.

Finally, it is to be understood that the above-described embodiments are intended to illustrate rather than limit the invention. Variations may be made to the embodiments without departing from the spirit of the invention as claimed. The above-described embodiments illustrate the scope of the invention but do not restrict the scope of the invention.

It is also to be understood that the above description and the claims drawn to a method may include some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps. 

1. A method for making a carbon nanotube composite preform, the method comprising: providing a substrate; forming a plurality of carbon nanotubes on the substrate; placing the plurality of carbon nanotubes and the substrate in a solvent for a predetermined time; taking the plurality of carbon nanotubes and the substrate out of the solvent; and drying the plurality of carbon nanotubes and the substrate.
 2. The method as claimed in claim 1, wherein the solvent comprises at least one substance selected from the group consisting of water, ethanol, and oxydol solution.
 3. The method as claimed in claim 1, further comprising a step of evacuating gas entrapped in the carbon nanotube composite preform.
 4. The method as claimed in claim 3, wherein the gas entrapped in the carbon nanotube composite perform is evacuated by vacuum treating the plurality of carbon nanotubes and the substrate in the solvent.
 5. The method as claimed in claim 4, wherein a water-cycle vacuum pump is used in the vacuum treatments.
 6. The method as claimed in claim 4, wherein the vacuum treatments facilitate gas between adjacent carbon nanotubes of the plurality of carbon nanotubes migrating to ends of the plurality of carbon nanotubes away from the substrate.
 7. The method as claimed in claim 4, further comprising forming a plurality of honeycomb-shaped gaps by shifting the ends of the plurality of carbon nanotubes away from the substrate.
 8. The method as claimed in claim 7, wherein sizes of the honeycomb-shaped gaps range from about 2 micrometers to about 300 micrometers.
 9. The method as claimed in claim 4, wherein the vacuum treatments take about 10 minutes to about 60 minutes.
 10. The method as claimed in claim 4, wherein a ultrasonic vibration treatment is used in the vacuum treatments, and the ultrasonic vibration treatment takes about 10 minutes to about 60 minutes.
 11. The method as claimed in claim 1, wherein the drying is conducted in a vacuum drying oven.
 12. The method as claimed in claim 1, wherein the drying is conducted at a temperature in a range from about 40° C. to about 50° C.
 13. The method as claimed in claim 1, wherein the plurality of carbon nanotubes are formed substantially perpendicular to the substrate.
 14. The method as claimed in claim 1, the step of forming the plurality of carbon nanotubes further comprising arranging the plurality of carbon nanotubes in a preferred orientation.
 15. The method as claimed in claim 1, wherein the plurality of carbon nanotubes are formed by chemical vapor deposition methods or laser ablation methods.
 16. A method for making carbon nanotube composite preform, the method comprising: forming a carbon nanotube array on a substrate, wherein the carbon nanotube array comprises a plurality of carbon nanotubes substantially perpendicularly to the substrate; placing the carbon nanotube array and the substrate in a solvent for a predetermined time; evacuating gas between adjacent of the plurality of carbon nanotubes out of the carbon nanotube array, and enlarging gaps between ends of the plurality of carbon nanotubes away from the substrate; drawing the plurality of carbon nanotubes and substrate out of the solvent; and drying the plurality of carbon nanotubes and the substrate.
 17. The method as claimed in claim 17, wherein a vacuum treatment is used, and the gas forms a plurality of gas pockets on the ends of the plurality of carbon nanotubes away from the substrate under the vacuum treatment.
 18. The method as claimed in claim 18, further comprising forming a plurality of honeycomb-shaped gaps by surface tensions of the plurality of gas pockets. 